The present invention relates to an electronic-circuit assembly and the manufacturing method thereof, particularly, to an electronic-circuit assembly and the manufacturing method thereof including a substrate upon which an electronic device is provided and other substrate which the former substrate is mounted.
An example of a conventional electronic-circuit assembly is disclosed in U.S. Pat. No. 5,203,075. The electronic-circuit assembly shown in FIG. 10 of the reference has a substrate 13 upon which a flexible substrate 31 is mounted. The flexible substrate 31 is connected by solder to the substrate 13. Specifically, the through-hole on the flexible substrate 31 is connected by solder to the pad on the substrate 13. In order to make the flexible substrate 31 and the substrate 13 parallel, a frame 47 is set in the peripheral portion between the flexible substrate 31 and the substrate 13. An LSI device 3 is provided on the flexible substrate 31. Nothing other than both of the solder and the frame 47 is provided between the flexible substrate 31 and the substrate 13.
The aforementioned conventional technology is faced with a problem that the flexible substrate may be poorly connected to the other substrate via solder. This problem is due to the flexible substrate not maintaining level, when or after the flexible substrate is mounted on the other substrate. Furthermore, the interval between the flexible substrate and the other substrate may not be kept even.
In addition, in the aforementioned conventional technology, there is also the problem that the device assembly is week to mechanical stresses or stress applied by the heat. The solder may come off causing breaking of the wire connections. These problems stem from the fact that the flexible substrate is only connected by solder to the other substrate.
Moreover, in the conventional technology, there is the problem that the device assembly is week to moisture. The solder which connections the flexible substrate to the other substrate may easily become weak, since the solder is exposed to a moist atmosphere. That is due to the fact that the solder connecting the flexible substrate to the other substrate is directly exposed to the open air. Moreover, there is also the possibility that a moist atmosphere causes migration to occur more easily.